2. It is used to taunt a girl when she does something stupid or ridiculous but imagines that she has done something remarkable or heroic, and is well pleased with herself about it.
The girl taunted is expected to correct herself or give an explanation for what she has done after this is said to her.
The taunt can be followed by further questioning using "why," "what," when" or how."
When you want to taunt a guy, you say "Hello hero!?"

Examples:

1. A hot girl stands close by at a party and you say "Hello heroine. Wanna dance with me?"

2. You are sitting in your friend's car and your friend overtakes other cars at 90 miles/hour by changing lanes in a ridiculous zigzag manner and you say to her "Hello heroine!? What are you doing? We could have gotten into an accident there."
Your friend cockily replies "But we didn't, did we?"